1. Technical Field
The present invention relates to a display apparatus and method, and more particularly to a display apparatus and method suitable for display of moving images.
2. Background Art
There is a demand for improving the quality of displayed images, as by improving signal processing techniques and driving techniques for image display devices.
In general, the image quality of an image can be improved by increasing the resolution of the image and smoothing the texture thereof. The amount of information of an image is expressed in the unit of pixels indicative of dots (dots) which constitute the image. The number of pixels of an image is expressed by the number of horizontal and vertical dots of the image, such as 800×600 or 1024×768. More specifically, the greater the number of pixels (dots), the more smooth the texture of the image and the more the amount of information constituting the image.
To display an image with high resolution, there is a technique (refer to Patent Document 1, for example) which makes it possible to display an image with twice as high resolution in a multi mode compared to a system using only one display, by using, for example, two displays 1 and 2 so as to cause the display 1 to display an image in a normal single mode and so as to cause the respective displays 1 and 2 to display the left and right halves of the image in the multi mode.    [Patent Document 1] Japanese Patent Application Publication No. Hei-10-124024
If an image is displayed with increased resolution, the amount of information constituting the image increases, so that the amount of data to be transferred to the display 1 or 2 increases and the data transfer rate needs to be increased. For this reason, this system is constructed to perform transfer of image data without increasing the data transfer rate, by reducing the amount of data for each dot of the displays 1 and 2 and performing conversion of the reduced data through signal processing.
In addition, the image quality of a moving image in particular can be improved by increasing α frame rate which is the number of times per second of updating of a screen.
For example, when a moving image is to be projected and displayed on a screen by using a projector, the projector displays α frame image line by line by performing horizontal scan on a line by line basis, and after having scanned all lines of one frame of image, starts scanning image data of the succeeding frame, thereby displaying the moving image.
As mentioned above, the image quality of a moving image in particular can be improved by increasing the frame rate. However, in order to perform display processing according to high frame rates, it is necessary to increase the processing speed of a driving circuit for driving a display device, and furthermore, it is necessary to increase the reaction speed of a light-amount modulation element which determines the intensity of an image. This method is technically difficult, and results in an increase in cost.
Although it is known that the image quality of a moving image can be improved by increasing the frame rate, it is impossible to actually examine the relationship between the frame rate and the image quality of the moving image at increased frame rates. Accordingly, it has not yet been clear whether it is possible to improve the image quality of a moving image to an unlimited extent by increasing the frame rate to an unlimited extent.
As a matter of course, it has been impossible to quantitatively understand the relationship between the frame rate and the moving image at increased frame rate.
For this reason, the present inventor noticed the frame rate of the next generation digital cinema format, and examined its necessary limitations in terms of visual characteristics.
It has heretofore been considered that the speed of a pursuit eye movement which is called smooth pursuit coincides with the moving speed of a visual target. Westheimer has stated that the eyes move at the same speed as the speed of a visual target which is not higher than 30 deg/sec (Westheimer, G., A. M. A. Arch. Ophthal. 52, pp. 932-941, 1954).
However, later researches have demonstrated that the speeds of pursuit eye movements are in almost all cases smaller than the speeds of visual targets. Meyer, et al. have stated that the pursuit speed of the eyes is approximately 0.87 with respect to the speed of a visual target. (Meyer, C. H. et al., Vision Res. Vol. 25, No. 4, pp. 561-563, 1985).
Although Meyer has reported that a maximum pursuit speed limit of 100 deg/sec was obtained, Meyer has stated that such a pursuit speed was a result obtained from skilled test subjects and general test subjects were unable to perform such tracking. The condition of this experiment is a visual distance of 80 cm which greatly differs from the visual environments of movie theaters. The visual target is a light spot which moves by a galvanometer, and Meyer does not discuss the spatial frequency of the visual target.
In Japan, there is a report example of NHK which discusses frame rates (Yasushi Tadokoro, et al., NHK Technical Report, September (1968), pp. 422-426, 1968), but the condition of the report is a 14-inch monitor with a maximum luminance of 30 fl (102.78 cd/m2) at a visual distance of 7H (H: screen height) and still does not allow for cinematic conditions. In addition, the report concludes that a field frequency of 60 Hz or higher is unnecessary for the reason why large motion does not appear in general contents. The conditions of Miyahara's experiment on dynamic visual acuity with respect to vibrating visual targets are a 14-inch monitor, a visual distance of 4H and a maximum luminance of 400 cd/m2. Experiments concerning visual characteristics have been mainly conducted under visual environment conditions such as comparatively short distances and high luminances.
Therefore, the present inventor has conducted experimental examinations on the dynamic spatial frequency characteristics of the eyes in the visual environments of movie theaters, i.e., a maximum luminance of 40 cd/m2 and a visual distance of 5 to 15 m. Research on moving image quality depending on such dynamic spatial frequency characteristics is important because such research leads to a great consideration of conventional formats for frame rates.
In the process of this research, the present inventor has actually examined the relationship between frame rates and moving image quality in higher frame rates and demonstrated human visual characteristics.
The present invention has been made in view of the above-mentioned situations, and intends to make it possible to present a moving image of less degradation to an observer who is a person viewing a displayed moving image, on the basis of human visual characteristics without unnecessarily increasing the frame rate.